I rented a HD Road-King from Las Vegas Harley Davidson
www.lvhd.com last weekend. It was about $200/day.
[EDIT]The price was quoted at $155/day, but after taxes and the premium insurance package ($29/day) it all came out to $196.01/day with no discounts at all.[/EDIT]
Las Vegas Harley Davidson was very convenient and helpful. They provided maps and itineraries for day trips, etc. I would definitely use them again if I were going to rent another Harley.
While I disliked the bike very much, I was very happy with the experience. My passenger was comfortable, too.
They provided only half-helmets. You should bring gloves and sunglasses or goggles, and don't forget that you might be riding at night. Don't just throw your sunglasses into the hard luggage, as the excessive vibration will scratch the hell out of the lenses and ruin them.
Also, be aware that in Las Vegas, "right around the corner" means about 5 miles away.
Have fun!
Ed